Re: [PATCH 10/18] nvme-tcp: fixup send workflow for kTLS

Hannes Reinecke
2023-03-30T17:26:33Z

On 3/30/23 17:24, Sagi Grimberg wrote:
>
>> kTLS does not support MSG_EOR flag for sendmsg(), and in general
>> is really picky about invalid MSG_XXX flags.
>
> CC'ing TLS folks.
>
> Can't tls simply ignore MSG_EOR instead of consumers having to be
> careful over it?
>
>> So ensure that the MSG_EOR flags is blanked out for TLS, and that
>> the MSG_SENDPAGE_LAST is only set if we actually do sendpage().
>
> You mean MSG_SENDPAGE_NOTLAST.
>
> It is also a bit annoying that a tls socket dictates different behavior
> than a normal socket.
>
> The current logic is rather simple:
> if more data comming:
>     flags = MSG_MORE | MSG_SENDPAGE_NOTLAST
> else:
>     flags = MSG_EOR
>
> Would like to keep it that way for tls as well. Can someone
> explain why this is a problem with tls?

TLS is using MSG_EOR internally (to control the flow of the underlying
tcp stream), so it's meaningless for the ULP.
I've no idea about SENDPAGE_NOTLAST; that one is particularly annoying
as we have to check whether we do sendpage() or sendmsg().

But TLS really should blank out invalid flags, as it has different rules
for them than anyone else. And the caller really shouldn't be burdened
with checking whether TLS is enabled or not.

Cheers,

Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
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